Whether you’re trying to go green to save money or reduce your carbon footprint, it helps to know where to focus your efforts. It makes little sense to spend a lot of effort saving a few kilowatt hours on appliances that mean very little while ignoring the appliances that consume more electricity. By using a wattage meter such as the P3 International P4400 Kill A Watt Electricity Usage Monitor, you can pinpoint the appliances that are the most power hungry.
I recently had the opportunity to test various devices and the results were pretty much inline with what I had expected. In most homes, the refrigerator is the 2nd biggest consumer of electricity behind the air conditioner. Since I don’t have an air conditioner, the refrigerator is my biggest power hog. My very old refrigerator was surprisingly energy efficient drawing about 1.8 kwH/day which translates to about 657 KwH/ year.
There’s two main ways to measure electricity use. Wattage and kilowatt hours. Wattage gives a quick real time view of what the device is drawing at the moment but this measurement is ineffective with appliances that contain a thermostat such as a refrigerator or heater. That’s where the kilowatt hours meter comes in handy. Set the meter to this mode and leave it on for a typical day. Take the results and multiply by 365 to get the yearly power usage. From there, simply multiply this number by your average cost per kilowatt hour to see how much this appliance cost to run per year.
After learning my computer draws 7 watts when completely off and 10 watts while asleep, I will now either put it to sleep or turn off the power at the power strip if I want it completely off. Shutting down the computer without cutting power results in an insignificant savings. Another revelation is my 19” lcd monitor draws 25-30 watts so I changed my monitor power down time to 3 minutes from 15 minutes. With lcd monitors, it comes back on almost immediately so powering it down frequently is no problem. I also have a small space heater which draws about half the kilowatt hours per day as my refrigerator even on the lowest setting to provide a minimal of heat.
Here are some wattage numbers for selected devices.
- Refrigerator – 170 watts when cooling, 15 watts on standby.
- Dual core computer with 1 SSD and 1 7200 rpm drive – 75 watts
- Computer with monitor on – 100 watts
- Computer with monitor on and 1 external usb drive on – 110 watts
- Computer running at 100% cpu while encoding h.264 video file – 130 watts
- Computer in sleep mode – 10 watts
- Computer turned off but connected to power strip – 7 watts
- Computer speakers w/ sub-woofer – 6 watts with and without playing sound
- iPad charging – 6 watts
- Uninterruptible power supply on with no load – 8 watts
- Dustbuster vac charging – 5 watts
- 20” lcd hd tv – 20 watts
- Ryobi 14.4 volt drill charging base – 27 watts charging, 2 watts standby.